Liquid crystal displays (LCDs) are display devices that control transmission/reflection of light (ON/OFF of display) by controlling the alignment of birefringent liquid crystal molecules. One way to align liquid crystal molecules is to adopt a structure in which an alignment film subjected to an alignment treatment such as a rubbing treatment or a photo-alignment treatment is located in contact with a liquid crystal layer.
Alternatively, like in the multi-domain vertical alignment (MVA) mode, the alignment of liquid crystal molecules may be controlled by means of bank-like protrusions of a dielectric material extending in an oblique direction on a common electrode, slits parallel to such bank-like protrusions on pixel electrodes, or the like structures, without performing any alignment treatment.
In the case of an MVA mode liquid crystal display device, liquid crystal molecules are in the vertical alignment to a substrate surface while no voltage is applied. Once a voltage is applied between a pixel electrode and a common electrode, the liquid crystal molecules become tilted at an angle corresponding to the voltage applied. In each pixel, there are some regions (domains) in which liquid crystal molecules are tilted in different directions due to slits on pixel electrodes or bank-like protrusions. These regions, in which liquid crystal molecules are tilted in different directions, in each pixel provide better display quality.
Disadvantageously, the regions with slits or protrusions tend to have lower light transmittance. The light transmittance can be increased by simply arranging such bank-like protrusions or pixel electrode slits with larger intervals. However, too large intervals between bank-like protrusions or slits prolong the time required for a change in the angles of all liquid crystal molecules, and therefore lead to a very slow response speed of the liquid crystal molecules to application of a voltage necessary for display to a liquid crystal layer.
A technology to improve the response delay has already been put into practical use. Specifically, in this technology, a polymer layer memorizing tilt directions of liquid crystal molecules is formed on an alignment film by injecting a liquid crystal material containing polymerizable monomers between substrates, and polymerizing the monomers while applying a voltage (hereinafter, this technology is also referred to as “PSA (polymer Sustained Alignment) technology”) (see, for example, Patent Documents 1 and 2).    Patent Document 1: JP 2003-307720 A    Patent Document 2: JP 2008-076950 A